The present invention relates to a worm type compressor for compressing gaseous fluid such as air, refrigerant gas, etc. therein.
The present invention provides a small-sized worm type compressor having the above described construction which operates silently and exhibits excellent durability.
Hereinafter, gaseous fluid will be called "fluid."
We, inventors, have developed a small-sized worm type fluid rotating machine (Japanese patent application No. 39940/1978, U.S. patent application Ser. No. 26,730 now abandoned).
According to the above machine, a worm is composed of a cylindrical body provided with a plurality of spiral-like passages in its inner periphery and a rotor is coaxially and slidably inserted within the worm. And within the rotor, a pinion gear is provided so as to rotate about an axis perpendicular to and spaced from the axis of the rotor. In the outer periphery of the pinion gear, teeth are formed. One portion of the teeth of the pinion gear is projected from the rotor to be engaged with the spiral-like passages of the worm. Thus, fluid sealing chambers are formed by the spiral-like passages of the worm, teeth of the pinion gear and the outer periphery of the rotor. As the worm and the rotor are relatively rotated, the teeth of the pinion gear travel within the spiral-like passages, and the volume of each of fluid sealing chambers is varied to compress the fluid therein.
In the worm type fluid rotating machine having the above described construction, an internal fluid outlet port opens at the outer periphery of the rotor so as to be opposed to each of the finishing ends of the fluid compressing side of the spiral-like passages. And when the rotor and the worm are relatively rotated, the internal fluid outlet port passes each of the finishing ends of the spiral-like passages in turn and immediately after that time, each of the teeth of the pinion gear which travels within the spiral-like passages, compressing the fluid therewithin, passes each of the finishing ends of the spiral-like passages.
The worm type rotating machine having the above construction has the drawback that one portion of the fluid which is compressed by each of the teeth of the pinion gear and is discharged from the internal fluid outlet port, leakes into the low pressure side of each of teeth of the pinion gear in the final stage of the fluid compressing step.
In order to overcome the above drawback, the following construction may be adopted. Namely, the internal fluid outlet port is provided in the rotor so as to pass each of the finishing ends of the spiral-like passages before each of the teeth of the pinion gear passes each of the finishing ends of the spiral-like passages. As a result, in the contact surface of the inner periphery of the worm and the outer periphery of the rotor and between the fluid outlet port which has already passed each of the finishing ends of the spiral-like passages when each of the teeth of the pinion gear passes it, and each of the finishing ends of the spiral-like passages, there is formed a sealing portion having length enough to prevent the compressed fluid from leaking into the low pressure side of the spiral-like passages.
However, in the compressor provided with the sealing portion, after the outlet port which discharges the compressed fluid passed each of the finishing ends of the spiral-like passages, the remaining fluid within the fluid sealing chamber is further compressed by each of the teeth of the pinion gear which is approaching to each of the finishing ends of the spiral-like passages.
Furthermore, in the worm type fluid rotating machine of this type, lubricating oil is used to lubricate the gaps between the spiral-like passages of the worm and the teeth of the pinion gear and to improve the sealing effect of the sliding portions of the machine.
The lubricating oil is also compressed in each of the finishing ends of the spiral-like passages which has been already cut off from the internal fluid outlet port, together with a compressed fluid in the final stage of the compressing step.
Since the lubricating oil has incompressibility, extremely high pressure occurs suddenly in each of the spiral-like passages. When the extremely high pressure occurs, abnormal noise generates and the pinion gear is likely to be bent or broken in its teeth portion which is the weakest portion in the fluid rotating machine.
Accordingly, an object of the present invention is to provide a small-sized worm type compressor.
Another object of the present invention is to provide an improved worm type compressor wherein the pressure within each of the spiral-like passages is prevented from being increased abnormally in the final stage of the compressing step.
Still another object of the present invention is to provide an improved worm type compressor which operates silently and exhibits excellent durability.